Sub-atmospheric wound care system

ABSTRACT

Methods and systems are provided for a sub-atmospheric wound-care (SAWS) system for treating an open wound. The SAWS system includes a regulated vacuum source for developing a negative pressure, a flow rate meter configured to measure a flow rate of liquid removed from the wound, a primary pressure regulating sensor located proximate the wound for directly measuring the negative pressure at the wound, a backup pressure regulating sensor located vacuum tube, a porous dressing suitable to be sealed airtight which is positioned within a wound interface chamber, a collection canister configured to collect said liquid removed from the wound, and an adapter configured to use wall suction a primary regulated vacuum source.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, claims priority from, andhereby incorporates by reference in its entirety, U.S. patentapplication Ser. No. 11/875,668 filed on Oct. 19, 2007 which claimspriority from U.S. provisional application 60/853,000.

BACKGROUND

1. Field of the Invention

The present invention relates to patient wound care, and morespecifically to systems and methods of wound coverings and dressings.

2. Description of Related Art

The use of negative pressure or vacuum to heal wounds has gained greatacceptance over the last 2 decades. Negative-pressure wound therapyinvolves the application of a vacuum to a sealed wound dressing in orderto facilitate the healing properties of an open traumatic or chronicsoft tissue wound. These types of wounds occur acutely from injury or aspart of a chronic disease, like diabetes mellitus. An open wound is awound that is not able to be closed side-to-side by direct suture repairfor some reason. These reasons include but are not limited to thedimensions/size of the wound, the level of contamination or infection inthe wound. Wounds of this sort are very common in combat casualties.They represent the single most common injury pattern seen in soldierselevated to Echelon V level of healthcare.

While the value of vacuum assisted wound healing has been known fornearly one-half century, this form of wound care technology was firstmarketed in the U.S. market in the early 90's by Kinetic Concepts, Inc.(KCI)—the Wound V.A.C. More recently, Blue Sky Medical, Inc. hasreleased a negative pressure wound therapy device, the Versatile 1,which is based on concepts of negative pressure therapy that werepublicly known. Both the KCI and Blue Sky Medical products, however, aresubject to several key deficiencies. These deficiencies of conventionaldevices have apparently not been recognized as problems in the art,since they remain unaddressed.

A negative pressure wound care device typically includes a regulatedvacuum source, tubing and collection canisters, and a porous dressingthat can be sealed airtight. Negative pressure wound systems are used totreat open wounds either chronic as seen in conditions like diabetes oracute from trauma. Traditionally these wounds were treated with cottongauze dressings which had to be changed three times per day. Thesechanges were very painful to the patient and cost a significant amountof nurse and/or doctor labor hours. On the other hand, vacuum wounddressings can be left in place for several days, they are changed in theoperating room (OR) so the patient is not awake and they essentiallytake care of themselves. This form of dressing reduces labor consumptionand accelerates wound healing, often by 50% or more. However,conventional vacuum wound care devices are subject to a number ofdrawbacks giving rise to false failure alarm and increasedsusceptibility to patient infections.

SUMMARY

Embodiments disclosed herein address the above stated needs by providingsystems and methods for a sub-atmospheric wound-care (SAWS) system fortreating an open wound. Various embodiments of the SAWS system include aregulated vacuum source configured to develop a negative pressure, aflow rate meter configured to measure a flow rate of liquid removed fromthe wound, a pressure regulating sensor configured to be locatedproximate the wound for directly measuring the negative pressure at thewound, a collection canisters configured to collect said liquid removedfrom the wound, a porous dressing suitable to be sealed airtight, and anadapter configured to use wall suction a primary regulated vacuumsource.

Other embodiments provide a brushless vacuum motor for use as a secondregulated vacuum source, and a valve to switch between the firstregulated vacuum source and the second regulated vacuum source. Variousembodiments provide an electronic-programmable vacuum regulator whichaccess the vacuum path between the wound interface chamber and theregulated vacuum source. The electronic-programmable vacuum regulatorserves as the controller for the SAWS system.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof the specification, illustrate various embodiments of the invention.Together with the general description, the drawings serve to explain theprinciples of the invention. In the drawings:

FIG. 1 depicts an exemplary embodiment of the Sub-Atmospheric Wound-careSystem in a typical clinical setting;

FIG. 2 depicts the electronic-programmable vacuum regulator (EVR) inaccordance with various exemplary embodiments of the SAWS;

FIG. 3 depicts a cutaway view of the tubing interface chamber inaccordance with various exemplary embodiments of the SAWS; and

FIG. 4 is a flowchart of an exemplary method of using the SAWS system inaccordance with various embodiments.

DETAILED DESCRIPTION

FIG. 1 depicts an exemplary embodiment 100 of the Sub-AtmosphericWound-care System (SAWS) in a typical clinical setting. Variousembodiments of the present invention adopt novel and useful approaches,as compared to conventional devices, for each of three components of theSAWS negative pressure wound care system.

Various embodiments of SAWS are configured with a flow rate meter 101 tomeasure the flow rate of liquid removed from the wound. This helps toavoid the danger of unwitnessed exsanguination, a rare but potentiallylethal threat with conventional devices which have no early means fordetecting accelerated fluid outflow from the wound. For example, insituations where an injured artery starts to bleed under the wounddressing, conventional devices have no similar dedicated warning system.Without a flow meter 101 and high flow alarm, conventional devices haveno means for alerting medical staff to a potential vascular leak orexsanguination event. Problems such as conventional devices suctioningsanguineous fluid from arterial leaks are not detected until thecollection canister of the conventional device is full. This delayedresponse system can significantly compromise a patients outcomefollowing a vascular leak under a placed negative pressure dressing. Therecorded flow rates provide a valuable metric for physicians, andgathering this type of data is an improvement in the use of negativepressure wound care systems.

The provision of the flow meter 101 in the SAWS device allows for theuse of larger canisters 103, since warning alarms no longer need todepend on the canister filling to capacity. Typically, the canisters onconventional devices are small (e.g., 250 cc). The SAWS device may beequipped with larger, more economical generic sized canisters 103 (e.g.,1,000 cc) since SAWS has a flow meter 101 to detect excessive fluid flowrates. This helps to reduce nursing demands. Moreover, canister changesrequire that the suction is turned off for as much as 15 minutes.Turning suction off to the dressing during this period risks leakingwound fluid onto the adhesive seal, ultimately, ruining its adhesion andrequiring replacement of the entire dressing. Thus, the larger canisters103 of SAWS, which require fewer canister changes, aids in wound care.Various sizes of canisters may be used with SAWS, in addition to (or inplace of) the 1000 cc canister. Typically, the canisters are made ofclear plastic with markings every 100 cc. Specialized appendages may beprovided to improve ergonomics and docking capability with the main EVR.The casing of the SAWS device is typically implemented with specializedappendages that securely fit a 1000 cc canister. Additionally there maybe retractable arms on the case suitable for securing the EVR to the bedrails during patient transfers. An easy to carry handle will also beincorporated.

With the flow meter 101 of the SAWS, an automatic shut-off system can beplaced that will sound an alarm and cut suction whenever a dangerousrate of fluid removal is recorded (e.g., 50 cc/min or 200 cc/10 min, orother parameter set by the individual provider). Various algorithms forresponse can be engineered to meet customer specifications. For example,immediately following dressing placement, this alarm can be suspendedfor a period, as there typically is a larger amount of fluid suctionedin the first 5 minutes of use.

There have been occasions in the use of conventional negative pressuresystems where patients nearly exsanguinated in their hospital bedroomsbecause a vessel injury in the vicinity of the conventional deviceruptured and arterial bleeding was suctioned up by the device. Theconventional VAC systems have no means for recording the rate of flow offluid from the wound. The only alarm that is generated in this situationis a “Full Canister” alarm, however this may not be activated until thepatient has already lost 1-2 or more units of blood. The SAWSincorporates a liquid flow detecting sensor that will activate alarmsfor high flow rate at certain levels. Default levels will be set atmanufacturing, however the device will have a menu access that allowsthe individual provider to set his or her own desired parameters. Inaddition to protecting against this rare, but potentially lethal event,a flow meter will provide the physician with an automated measure of theone value that needs to be recorded whenever a drainage system is usedon the body—the amount of fluid removed. Outputs for traditional timeperiods (e.g., 8 hours or shift and 24 hours) can be displayed on theLCD screen. Automating outputs will eliminate this traditionally tediousnursing task and improve the accuracy of this data point. Accuraterecording of fluid outputs from trauma patients with large open woundsor burns is very important.

Various embodiments of SAWS cycles through a low suction state ratherthan a zero suction state during intermittent suction mode. Intermittentsuction (ramping from high to low vs. maintaining a constant set suctionlevel) has been shown in animals to be most effect. However, this modeof therapy is often painful for patients, as the suction is reapplied itforces the sponge or wound filler against the wound. The conventionalmachines reduce to zero suction during intermittent mode cycling, thusproducing the most pain. The dressing sponge fills with air and thencontracts again when the full suction is resumed.

Since various embodiments of the SAWS intermittent suction mode does notreach zero, it helps to reduce the pain associated with this mode ofnegative pressure therapy. Reducing or eliminating the pain previouslyassociated with the intermittent mode may encourage use of this mode,which may in turn improve the efficacy of negative pressure therapy.Likewise the ramp up interval, whether at the beginning of continuousmode therapy or with each intermittent mode cycle, will be controllableby the physician, or may be set to a default value (e.g., 5 to 30seconds). In some embodiments the default ramp up interval may be set to15 seconds, to allow more gradual increase in negative pressure as thedevice turns on. In addition, the SAWS device has a timer for recordingthe time of use, an important parameter for the physician. The timeralso provides a means for automating rental time use, which is animportant form of distribution for this device. Lastly, the LCD displayhas an area that displays the current time. The conventional devices donot have similar clocks or timers.

Various embodiments of SAWS use wall suction as its primary vacuumsource, which removes the noisy vacuum generating process from the room.The SAWS unit may be connected to the wall suction source with aconnector configured for such purpose. The use of wall suction greatlyimproves patient satisfaction, especially at night when the intermittentbuzz of the vacuum unit on conventional devices disturbs sleep. Further,the use of wall suction can avoid frequent device alarms which may bedue to overloading the vacuum motor of conventional devices. The vacuummotors of conventional devices are designed to be small in order to bemobile. Consequently, they have a limited suction capacity, especiallywhen compared to the wall suction source. This means when leaks aredetected and the pump is activated, the ability to respond and clear airquickly and efficiently may be compromised in conventional devices.Further, various embodiments of the SAWS use brushless vacuum motors astheir portable and back-up vacuum source. These motors tend to bestronger, more efficient and quieter than conventional motors.

Conventional devices rely solely on an internal vacuum motor forsuction. One drawback of this is that internal motors generate amonotonous buzz when they are active. Additionally, since the body'stissues are constantly dumping dissolved gas into the open wound, thevacuum will leak, regardless of the adhesive seal on the dressing. Inthe normal course of events, this leak, if detected by conventionaldevices, causes the internal motor to be activated in an effort togenerate sufficient suction to maintain the desired therapeutic level,thus producing an annoying noise. While this noise may seem minor, thebuzzing from this noise in the middle of the night significantlydisrupts sleep. The buzz evident in conventional systems is to bereduced in various embodiments of SAWS through the use of brushlessmotors. An additional consideration of the motor is size. The motors ofconventional systems tend to be small in order to minimize the size forportability purposes. Small motors have a limited reserve, and when theyare connected in parallel to several wounds simultaneously they may beunable to clear the air volume needed to continuously maintaintherapeutic suction. Wall suction is produced by large generatorslocated in the basement of the hospital, the vacuum from thesegenerators is more than sufficient for the present purposes, and theirnoise is not heard in the patient's room.

The tubing system 105 in various embodiments of the present inventionhas been simplified, as compared to conventional devices, to removeconnectors which were always difficult to use and threatened thesterility of the operative field. The tubing in conventional systems isdifficult to work with because of poorly designed connectors thatconnect the sterile end of the tubing to the nonsterile end. Thistypically occurs about 3 feet from the wound. When you apply the woundvac during surgery on the lower extremities, this short distance ofsterile tubing section can cause nonsterile parts of the tubing to rubon and off the sterile parts of the surgical drapes, thus violating thesterile field. In various embodiments of the present invention theseconnectors are eliminated, while in other embodiments the connectors aremoved farther away from the wound (e.g., four feet, five feet, or atleast greater than three feet) to avoid the danger of compromising thesterile field.

The tubing system 105 in various embodiment of the present invention hasbeen simplified, as compared to conventional devices, to removeconnectors which were always difficult to use and threatened thesterility of the operative field. The tubing in conventional systems isdifficult to work with because of poorly designed connectors thatconnect the sterile end of the tubing to the nonsterile end. Thistypically occurs about 3 feet from the wound. When you apply the woundvac during surgery on the lower extremities, this short distance ofsterile tubing section can cause nonsterile parts of the tubing to rubon and off the sterile parts of the surgical drapes, thus violating thesterile field. In various embodiments of the present invention theseconnectors are eliminated, while in other embodiments the connectors aremoved farther away from the wound (e.g., four feet, five feet, or atleast greater than three feet) to avoid the danger of compromising thesterile field. Various embodiments of SAWS do not require that centralportions of the tubing to be connected by the physician. By contrast,conventional systems require the tube connecting to the wound to beconnected to the tube traveling to the collection canister. Theconnector on conventional systems is difficult to use, and moreimportantly, it typically winds up resting on the edge of the sterileoperative field. In this position, the connector, which is handled bythe circulating OR nurse (thus contaminated) when the tubes areconnected, can slide on and off the sterile OR field, creating potentialbreaks in the sterile field.

The tubing used in the SAWS system is arranged to provide a vacuum pathto the regulated vacuum source, e.g., either the wall vacuum source or avacuum motor (vacuum pump). The SAWS tubing may be off-the-shelfsurgical tubing, sterile packed for application in the OR. Thecollection canister may be off-the-shelf as well, so long as the propersize is available, e.g., 1,000 cc. At the distal (wound) end of thetubing is a specially designed bilayer wound interface chamber 107. Thisis the means by which the tubing connects with the dressing. Thischamber 107 allows for dispersion of the vacuum effect more equally overthe extent of the dressing. Further, the chamber 107 may be configuredwith two appendaged tubes with drainage holes in them. These flexible,small tubes can be aimed and placed by the surgeon down long and narrowwound tracts, like those seen in wounds sustained from gunshots orimprovised explosive devices. This helps to avoid the creation of occultdeep space infections that occur in devices that do not offer thisfeature. If these tracts do not exist in the wound, then the tubing neednot be used in the dressing.

In addition to functioning as a negative pressure wound dressing, theSAWS device can perform other functions. For example, for particularlypainful wounds, intermittent doses of dilute local anesthetic could berun through the instillation system to reduce the pain. Lastly, the SAWScan be used without the tubing and wound filler dressing. Instead deepclosed drains, like those placed with elective surgeries, can be hookedto the system and insure that a constant, regulated vacuum is beingmaintained. At the same time, the output for these drains can beautomatically recorded. Since the EVR is a reusable device, thisimproved surgical drain concept can be used with little to no additionalcost over that of the simple drains currently being used, which usemanually applied bulb suction and require the nurse to record outputs.

FIG. 2 depicts an exemplary embodiment 200 of theelectronic-programmable vacuum regulator (EVR) for the SAWS. Theelectronic-programmable vacuum regulator (EVR) is the human interfacewith the SAWS device, and as such, is connected or otherwise has accessto the vacuum path between the wound interface chamber and the regulatedvacuum source. Various embodiments of the EVR contain an automatedpressure valve that is controlled by internal software. This valve maybe opened and closed in response to two pressure sensors thatcontinuously monitor the negative pressure (vacuum) being applied to thewound. The intake end of the valve is typically configured to acceptflow from either the hospital wall vacuum source or from an on-boardbrushless vacuum motor. Typically, the primary vacuum source for thisdevice is the wall vacuum source. The on-board motor is there as aback-up should the primary source fail. Additionally, it will serve asthe primary source when patients need mobility within the hospital. Aconnector is provided on the SAWS device for connection to the wallvacuum source.

The EVR has an LCD screen that displays various parameters such as:current actual pressure in the dressing, programmed or desired pressure,alarms and alarm status, time, and output. These parameters arediscussed in the following paragraph. In various embodiments the frontface of the EVR is configured with an LCD display of approximately 3″×1″size, with touch panel buttons. The buttons include an up arrow, downarrow, on/off, menu, enter and backlight button as shown in FIG. 2.These are used to program specific features and adjust the itemsdisplayed on the LCD screen.

The EVR displays the current actual pressure in the dressing, asdetermined by the SAWS dual pressure sensing technique which allowsaccurate and continuous pressure monitoring at the wound, with a back-upapproximation measurement being taken in the tubing. The wound levelpressure sensor allows the SAWS system to directly record the negativepressure at the wound, rather than approximating it by only measuringthe tubing pressure, as is done in conventional systems.

The EVR also displays the programmed or desired pressure. The physiciangenerally sets the desired parameter based on clinical use andexperience within a predetermined safe-range. One reason for twodifferent pressure displays is that, in practice, when there are leaksor problems with the system the actual pressure may not be the same asthe desired pressure. If this state exists longer than a predeterminedamount of time (e.g., 15 seconds), an alarm will alert the healthcareprovider of this situation, which is likely due to a leak. The SAWS hasa unique automated leak response algorithm that automatically increasessuction in the system briefly when a leak is detected. This reactionwill typically re-seal the leak in the adhesive seal. This automatedresponse obviates the need for the provider to evaluate the system, thusreducing the total number of alarms and the amount of labor required tomaintain the therapy. In the event that the leak persists or recursimmediately, then the leak alarm engages and the provider will have toaddress the situation. The provider can then come and evaluate thesituation. Typically, when a leak occurs there will be an audiblefailure (hissing noise) in the wound dressing seal and additionalocclusion adhesive dressing can be applied. In rare instances when thesystem continues to fail, the dressing can be removed at bedside and an“old fashioned” cotton gauze dressing can be applied.

Various embodiments of the SAWS device is equipped with a number ofalarms and displays the alarms as well as the alarm status. For example,alarms may be provided for: leak (lost suction, with continued airflow),blockage (reduced suction, with diminished or absent airflow), canisterfull and high flow rate (e.g., >50 cc/10 min, >100 cc/30 min, or othersafety parameters that can be programmed by the user). The combinationof these alarms and their sensors will detect system failures that canoccur with vacuum dressing therapy. Alarms will typically be configuredto blink on the LCD display and alarm tones will also sound, until theEVR is assessed by a provider. In addition to displaying alarms andalarm status the SAWS displays the time as well. This time displayserves as a consistent time piece for the provider, convenientlyavailable for recording usage time.

The SAWS has memories for recording various parameters at predeterminedor preset intervals. For example, the 8 hr and 24 hr output from thewound may be recorded automatically and displayed on the LCD screen.

Power for the SAWS may be supplied by an ordinary wall socket, with anoptional internal rechargeable (e.g., lithium) battery, for power incase of power failure or when the unit needs to be used a mobileenvironment. The tubing and wound dressing are all disposable and willbe packaged sterilely, but can be applied in a clean, nonsterile fashiondepending on the operational environment. Typically, the EVR is anon-disposable capital piece that will be encased in a hardenedenclosure that protects it from water or blunt force damage. Someembodiments of the EVR unit weigh less than 10 lbs and occupy a space ofless than 6″×6″×6″ in size. The EVR may be encased in high strengthplastic, which is watertight and hardened to survive drops from up to 6′onto concrete. Typically, the casing and hardware of various SAWSembodiments is hardened to the extent that it is designed to withstandat least a 6 foot fall onto concrete. Additionally, it is watertight toavoid damage from moisture. This will expand the life span of the SAWSdevices in both civilian and military uses.

Inside the SAWS case most embodiments include at least one circuitboard, sensors for leakage, blockage, flow rate, a brushless vacuummotor, a rechargeable battery and an automated switch that can directvacuum from the internal motor or the wall outlet through an automatedpressure valve that opens/closes in response to changes in the wounddressing's negative pressure. Additionally, there are outlets (oradapters) to receive power from wall outlets. A standard wall vacuumoutlet connector is typically positioned on the posterior aspect of theEVR. This connector may be configured to be retractable so that it canbe retracted when the internal motor is being used.

FIG. depicts a cutaway view of the tubing interface chamber 300 inaccordance with various exemplary embodiments of the SAWS. The chamber300 is the chamber 107 of FIG. 1. The tubing interface chamber of SAWSis bilayer, which maximizes the dispersion of the vacuum effect to allaspects of the wound similar to the way a shower head disperses water.Additionally it has suction tubes that can be routed into deeperportions of the wound (not shown). These modular suction tubes areintegral to the function of the interface chamber component. Thecombined modes of vacuum application to the wound filling material andwound bed, ensure the most symmetric distribution of vacuum to thewound. This, in turn, allows for the most optimal and complete drainageof the entire wound, which reduces the risk of occult infection. Tofurther reduce the risk of occult infection in narrow deep tracts ofwounds, the modular accessory suction tubes can be positioned into thesetracts. Conventional devices have no such ability.

The custom designed SAWS wound interface chamber may be embodied as adual-layer plastic air chamber with columns of plastic separating the 2layers into uniform air channels. Either end of this elliptically shaped(to match the longitudinal contour of most wounds) interface chamber maybe provided with docking ports for 8″ long flexible drainage tubes withmultiple perforations along their length. These accessory drains can bepositioned into narrow or deep parts of the wound, to improve suction tothese areas. These accessory drains are can be excluded, if they are notneeded. These accessory drainage tubes can be routed by the surgeon toareas of the wound that need more focused suction, or more importantlyto long narrow tracts in the wound. The conventional devices do not havethese accessory drainage tubes, thus a situation can and does occur inwhich long narrow dead spaces are created in the depths of the wound.These dead spaces become locations were fluids and bacteria cancoalesce. As a result, deep space infection can form under an otherwisewell functioning VAC dressing of conventional devices.

The configuration of the SAWS tubing interface chamber is distinguishedfrom the convention systems which use a “lily pad” tubing interface anddo not perform as well at diffusing the vacuum. That is, theconventional negative pressure wound treatment devices use a monolayerflange that results in the central portion of the wound receiving thehighest levels of suction while the periphery may not receive any. Oneconventional adapter, the KCI adaptor (“Lilly Pad”), is a sheet ofplastic that is fused into the terminal end of the tubing. Thisconventional adaptor has plastic nubs that are placed on its distalsurface. These are theoretically intended to disperse the vacuum as ithits the wound dressing. But since these nubs directly contact themoistened sponge, the dressing simply gets compressed into the nubs,thus negating any dispersion of vacuum. The SAWS uses a novel approachthat disperses the air in stable chambers, like a shower head, ensuringthat the vacuum is not simply dumped in the center of the dressing. Bydistributing the vacuum in the SAWS device, the periphery of the woundis exposed to the same level of vacuum as the central portion.

The SAWS dual pressure regulating sensors of various embodiments of thepresent invention are located in, or near, the wound, and in the tubingas well. The SAWS dual pressure sensing technique affords the accurateand continuous pressure monitoring useful for successful and reliablenegative pressure wound therapy. This wound level pressure sensor allowsthe SAWS system to directly record the negative pressure at the wound,rather than approximating it by measuring the pressure in the tubing, asis done in conventional systems. This approximation based on tubingpressure done in conventional systems becomes more and more inaccuratein infected wounds where secretions are thicker. This sensing techniqueis very dependant on several factors (sponge thickness, wound contours,fluid consistency, or the like), factors that can all reduce the actualamount of therapeutic suction reaching the wound. The failure ofpressure sensors in conventional devices to accurately control vacuumlevels in the dressing is not sufficient to allow use in military airevacuation flights. Currently, the U.S. Army prohibits use of vacuumwound care devices during air evacuation operations due to theunreliability of the current art.

The wound level pressure sensor in the SAWS is located between the woundand the dressing. By contrast, the sole pressure sensor in conventionalmachines is housed in the tubing of the device. Thus, the pressure beingsensed and displayed on the readout screen of conventional devices is anINDIRECT measure of the actual vacuum effect reaching the wound. Thesensor measures the pressure in the column of air leading up to thesponge. This measured pressure is as an approximation of the actualnegative pressure reaching the wound tissue. The thickness of thesponge, the depth and topography of the wound, the consistency of thesecretions and several other factors all effect the accuracy of thisapproximation. The SAWS uses a disposable pressure sensing disc toprovide feedback to the EVR. This DIRECT pressure measure will be usedto guide therapy. For the wound level pressure measurement a pressuresensor disc is placed between the wound and the wound filler. It istypically connected to a wire running along the tubing. This will be thepath of communication between this sensor and the EVR. Additionally, apressure sensor in the EVR will detect the air pressure in the tubing.The software may be programmed to analyze the changes of pressure in thetubing and at the wound margins and an algorithm will be created thatdirects the automated pressure valve to open/close to respond to changesin the negative pressure levels.

A second sensing apparatus measures pressure in the column of air in thetubing. Data from this second pressure sensor will be used to determineleaks, blocks and integrated with the wound surface sensor data toregulate the vacuum level in the system. The SAWS dual sensor systemtends to provide a more accurate pressure sensing mechanism, thusovercoming the failures of the conventional machines to maintaintherapeutic vacuum levels during the transport of casualties. Currently,casualties are not allowed to be transported with the conventional KCIwound VAC dressings, as they have a high rate of failure. Failure of anegative pressure dressing system turns these dressings into infectionproducers instead of reducers. Several examples exist of this systemfailure, prior to the current policy of no transport with the KCI VACdressings. This system will be designed specifically to overcome thissignificant drawback. Soldiers injured in Iraq are transported at leastthree times, and often several times, prior to making it to Echelon Vcare in the U.S. Each time, these soldiers have to be treated with “oldfashioned” cotton dressings, which are painful, seep and smell. It hascaused angst among US military surgeons who have to provide sub-optimaldressings to our servicemen, while the Iraqi combatants that don't gettransported, receive the state-of-the-art vacuum wound dressingsimmediately.

The wound filling material 301 of the SAWS system has been designedspecifically for a negative pressure wound care application. Thisnon-woven wound filler covers the wound surfaces, keeping the surfacesmoist, while separating the wound from the overlying adhesive andproviding a media which has preserved random pattern air channels thattends to disperse the vacuum equally to the wound surface. The woundfilling materials used with conventional devices are typicallyoff-the-shelf materials, and as such, are often subject to certaindrawbacks because they are not specially designed for the purpose. Forexample, the KCI Wound V.A.C., uses an off the shelf filter sponge thatis formed with open cell technology. This manufacturing process createsair filled cells throughout the sponge. When this conventional type ofsponge is cut, these cells are randomly intersected. Due to the geometryof the cells, some cells are cut and leave dangling free edges, whichcan be captured by the wound tissue and remain trapped in the wound,when the dressing sponge is removed. This causes an inflammatoryreaction occurs around these retained fragments of sponge. Moreover, theconventional sponge filters are typically 1″ thick, which is too thick.The conventional filter sponges tend to clog with thick fluids. Whenthis occurs the areas beneath these clogs do not get therapeutic levelsof suction. For another conventional device, the Verstaile 1, it isrecommended that cotton gauze dressing be used. Cotton is an absorbentand porous material, unlike the polymers used in the SAWS wound filler.Cotton products that remain in contact with the body for prolongedperiods can harbor bacteria which produce toxins that can injurepatients (e.g., toxic shock syndrome). Cotton gauze packing is typicallynot left in closed or sealed cavities in the body for this reason. Bycontrast, the wound filler 301 of various embodiments of the presentinvention is a non-woven polymer fiber that has no free dangling edges,thus obviating the aforementioned complications.

The SAWS specially designed non-woven wound filler material is placed onthe open wound surface, after the wound has been surgically debrided.The filler has malleability properties similar to steel wool, whichallow the material to be stretched from its resting, packaged state, tofill and match the contours of the wound without the need of surgicalinstruments to trim the material to fit. This novel material may beimpregnated with specially complexed silver ion molecules that candeliver sustained antimicrobial effect. A special silver impregnatedfine sheet netting can be placed between the wound filler and the woundsurface to prevent in-growth of the wound tissue into the wound filler.This will extend the life of each dressing, which will reduce theoverall number of dressings and operations to replace dressings. Thesilver impregnated fine mesh is particularly suitable for extended useapplications (e.g., >3 days). An adhesive may be used to seal thedressing to the skin margins and create an airtight (or near airtight)environment for the vacuum dressing to work. This adhesive will securethe wound interface chamber to the wound filler, thus completing thevacuum circuit.

The sponges used with conventional devices were not designedspecifically for negative pressure use. These conventional sponges arenonpliable—thus, scissors need to be used to cut the sponge to the exactcontours of the wound. This contouring/shaping step is often the longeststep in the entire wound dressing application process, usingconventional systems. Likewise, the standard sponge used withconventional devices is too thick. Fluids clot within the sponge andblock suction to areas of the wound. The novel SAWS wound filleraddresses these problems through its design. Since the SAWS material ismoldable, the surgeon can mold the dressing to fit the wound. The fillermay be formed to be thin enough to cover the wound. Further, thethickness of the filler can easily be adjusted by the physician, withoutthe need of surgical instruments. The SAWS wound filler material ispliable, but resists compression under typical conditions. For example,under vacuum, various embodiments retain a sufficient amount (e.g., 50%)of its thickness. Furthermore, the SAWS wound filler media hassufficient porosity to maintain adequate vacuum levels and drain fluidsfrom the wound, e.g., >60%.

Various embodiments of the SAWS wound filler media are bio-compatible,having no inflammatory response. Moreover, the media is indestructibleunder normal conditions to the extent that the fibers of the mediacannot be pulled free from the rest of the media. Various embodiments ofthe material are durable and do not dissolve due to contact with fluidor human tissue. The media is preferably stable in open air roomconditions for up to 1 hour, and at room to body temperatureindefinitely.

FIG. 4 is a flowchart of an exemplary method of using the SAWS system inaccordance with various embodiments. The method begins in 401 andproceeds to 403. In 403 a pressure sensor disc is placed on the woundsurface. Once the pressure sensor has been positioned the methodproceeds to 405. In 405 it is determined whether accessory drains are tobe used. If accessory drains are needed the method proceeds along the“YES” path to 407 and accessory drains are placed into deep, narrowportions of the wound. The proximal ends of these drains and thepressure sensor wire are then left out to the margins of the wound. Backin 405 if it is determined that no accessory drains are needed themethod proceeds along the “NO” path to 409.

In 409 it is determined whether netting is to be used with the SAWSdevice, e.g., a silver impregnated fine sheet netting for use betweenthe wound filler and the wound surface. Netting is used in somesituations to aid in preventing in-growth of the wound tissue into thewound filler. If netting is to be used the method proceeds from 409along the “YES” branch to 411 to position the netting. Once the silverimpregnated netting is in place the method proceeds to 413.Alternatively, back in 409 if it is determined that no netting is to beused, the method proceeds along the “NO” path to 413.

In 413 the wound filler is laid on a clean open wound, over the sensor.(In some instances, over the optional netting.) The SAWS wound filler isa malleable, porous substance, as described above. The wound filler maybe shaped to approximate the contours of the would. After the woundfiller has been properly positioned the method proceeds to 415. In block415 the wound interface chamber is placed centrally over of the woundfiller. In situations where accessory drains are used, their proximalends are folded back over the wound filler and connected to their portson the interface chamber. The pressure sensor wire is folded back overthe wound filler and connected to its mating wire on the tubing. Oncethe wound interface has been placed on the wound filler and connected tothe accessory drains (if any) the method proceeds to 417.

In 417 a clear adhesive is placed over the wound filler. The adhesivesecures the wound filler and interface chamber to the surrounding normalskin, which has been shaved and coated with a sticky substance, toimprove adhesion. Upon completing 417 the method proceeds to 419 toconnect the canister. The proximal end of the tubing is thrown off theoperative table and the circulating (nonsterile) OR nurse connects thetube to the 1000 cc collection canister. In 419 the EVR is connected tothe canister and to the wall vacuum outlet. Once all components of theSAWS are in place, the method proceeds to 423 and the EVR is turned onand the therapy is started. A successfully sealed and functioningdressing is confirmed, prior to completion of the case in 425.

Various components and/or activities may be included or excluded asdescribed above, or assembled/performed in a different order, with theinvention still remaining within the scope of at least one exemplaryembodiment. For example, in some embodiments the direct pressure sensor(positioned in block 403) may be placed over the screen netting, ratherthan directly on the wound. In some embodiments the EVR may be connectedto the wall vacuum (block 421) before connecting it to the canister(block 419), or, alternatively, before any of the activities precedingit as depicted in FIG. 4. Those of ordinary skill in the art know thatother such variations in implementing embodiments of the inventionexist, and are within the scope of at least one exemplary embodiment.

The use of the word “exemplary” in this disclosure is intended to meanthat the embodiment or element so described serves as an example,instance, or illustration, and is not necessarily to be construed aspreferred or advantageous over other embodiments or elements. Thedescription of the various exemplary embodiments provided above isillustrative in nature and is not intended to limit the invention, itsapplication, or uses. Thus, variations that do not depart from the gistof the invention are intended to be within the scope of the embodimentsof the present invention. Such variations are not to be regarded as adeparture from the spirit and scope of the present invention.

What is claimed is:
 1. A method of treating an open wound using asub-atmospheric wound-care system, the method comprising: positioning apressure sensor proximate the open wound; placing wound filler over theopen wound, said pressure sensor being located between the wound fillerand the open wound; placing a wound interface chamber over the woundfiller; and connecting a regulated vacuum source to the wound interfacechamber; wherein the regulated vacuum source is selected from a groupconsisting of a wall suction source and a portable vacuum source.
 2. Themethod of claim 1, further comprising: positioning a netting between thewound filler and the open wound, said pressure sensor being locatedbetween the netting and the open wound.
 3. The method of claim 1,wherein the netting is a silver impregnated mesh netting.
 4. The methodof claim 1, further comprising: positioning one or more accessory drainsover the open wound, said one or more accessory drains being suppliedwith suction from the regulated vacuum source.
 5. The method of claim 1,wherein the portable vacuum source is a brushless vacuum motor, themethod further comprising: providing a valve to connect the woundinterface chamber to either the wall suction or the brushless vacuummotor.
 6. The method of claim 1, wherein the pressure sensor is a firstpressure sensor, the method further comprising: providing a secondpressure sensor in a vacuum path between the wound interface chamber andthe regulated vacuum source.
 7. The method of claim 1, wherein thepressure sensor fits within a depression in the wound filler arranged toexpose the pressure sensor to the open wound.
 8. The method of claim 1,wherein the pressure sensor is a first pressure sensor, the methodfurther comprising: providing a second pressure sensor located in avacuum path between the wound interface chamber and the regulated vacuumsource.
 9. The method of claim 8, wherein the pressure sensor isconfigured to directly measure negative pressure at the open wound; andwherein the second pressure sensor measures a negative pressure in thevacuum path.
 10. The method of claim 1, further comprising: providing ascreen netting beneath the wound interface chamber on the open wound,wherein the pressure sensor directly measures negative pressure at theopen wound through the screen netting.
 11. The method of claim 1,further comprising: providing a first alarm configured to indicate thata predefined flow rate has been reached as detected by said flow ratemeter; and providing a second alarm configured to indicate that apredefined fluid level has been reached in a collection canister. 12.The method of claim 1, further comprising: providing a flow rate meteris configured to detect accelerated fluid outflow from the open wound.13. A method of treating an open wound comprising: shaping a wounddressing to fit over the open wound; placing the wound dressing within awound interface chamber; placing a pressure sensor within the woundinterface chamber said pressure sensor being located between the woundfiller and the open wound; positioning the wound interface chamber overthe open wound with the wound interface chamber covering the wounddressing and the pressure sensor; and connecting a vacuum source to thewound interface chamber.
 14. The method of claim 13, wherein the vacuumsource is a regulated vacuum source selected from a group consisting ofa wall suction source and a battery powered portable vacuum source. 15.The method of claim 14, further comprising: positioning a nettingbetween the wound dressing and the open wound, said pressure sensorbeing configured to directly measure negative pressure at the open woundthrough the netting.
 16. The method of claim 15, wherein the netting ismesh netting with an antimicrobial effect.
 17. The method of claim 13,further comprising: positioning one or more accessory drains over theopen wound, said one or more accessory drains being supplied withsuction from the vacuum source.
 18. The method of claim 13, wherein thepressure sensor fits within a depression in the wound dressing arrangedto expose the pressure sensor to the open wound.
 19. The method of claim13, wherein the pressure sensor is a first pressure sensor, the methodfurther comprising: providing a second pressure sensor located in avacuum path between the wound interface chamber and the vacuum source.